Which of the following are not associated with convergent plate boundaries? deep-focus earthquakes
rift valleys
island arcs (island building)
deep-sea trenches

poor water quality affects most estuarine organisms, including commercially important fish and shellfish. the pollutants that have the greatest impact on the health of estuaries include toxic substances like chemicals and heavy metals, nutrient pollution (or eutrophication), and pathogens such as bacteria or viruses.